Hi,
I have used a Fluke DMM with a Max/Min capture feature to measure the ringing voltage, not only red to green, but also red to ground (and green to ground).
To my surprise, the red wire to ground ringing voltage (some telephone equipment on line) was 93.2 VAC !! The green wire to ground ringing voltage was 36.4VAC. Note: Telephones are ringing.
Is this normal?
Thank You in advance, John
The internet is your friend.
Peter Wieck Melrose Park, PA
Wonderful explanation.
Hi, I saw that "sandman", and other places on the web, but it did NOT say anything about the ringing voltages from red to ground or green to ground.
That is why I made this post.
John
On Tuesday, January 21, 2020 at 7:26:22 AM UTC-5, snipped-for-privacy@verizon.net
ay
.a) Most POTS phones are two-wire these days. b) In most cases, the ground (separate) does not leave the demarc. c) Both the the "red" and the "green" are not at ground potential, *and* al so not at the same potential to each other.
Therefore the 'ring voltage' will be different from each to ground than bet ween the POTS conductors. Which was covered in the article linked, but not with these same words. Read carefully the section on measuring AC over DC, and that should help you understand.
Peter Wieck Melrose Park, PA
Try putting a 1K resistor in parallel with the meter. I predict that you will get something close to zero for both wires to your earth ground for both ac and dc measurements.
And it contained this little gem, which you all probably knew, but was a surprise to me:
***** A very good technical explanation for variances in AC voltage measurements was put out by Agilent (formerly HP), who makes their own meters ranging from handhelds to lab equipment. I was amazed to read that meter manufacturers calculate True RMS by reading the heat produced by the AC voltage (4 page PDF file): *****I could not get to the Agilent PDF just now.
There are ICs that calculate RMS for test equipment.
Agilent changed their name to Keysight several years ago.
Have something to add? Share your thoughts — no account required.
Ask the community — no account required